That ability boosts efficiency significantly, said Larry Nitz, executive director of transmission and electrification, while cutting only slightly into peak power output under wide-open throttle.

Reducing the noise, vibration, and harshness of the new engine was one primary goal, and GM workers who had ridden in test-mule Volts with the new powertrain said it was almost impossible to tell when the engine switched on.

The new engine has an aluminum block, compared to the cast-iron block of the current range extender, so overall weight of the new engine is no higher than that of the old one.

POWER ELECTRONICS

The new powertrain also has its power electronics, most significantly the inverter, built directly into the transmission rather than mounted separately on the car's body and connected by large orange high-voltage cables.

The inverter is smaller, lighter, and more efficient, and the integrated location contributes to a total weight reduction for the new powertrain of 130 pounds compared to the current generation.

LG Chem continues as the supplier of lithium-ion cells for the next Volt, but the latest generation of cells have 20-percent increase in volumetric energy density over the cells used in the 2015 Volt, which themselves were new this year.

The number of cells in the battery pack is cut from 288 to 192, still arranged in 96 modules and producing roughly the same total voltage.

The pack is slightly smaller in dimension, but its center of gravity is 10 mm lower and its weight is 30 pounds (13 kg) lower overall.

GM declined to specify the pack's total energy capacity (17,1 kilowatt-hours in the 2015 Volt) or the percentage of the pack that it uses (presently about 65 percent).

Nitz said, however, that the new pack had higher energy capacity and used more of it, presumably indicating an increase in the car's rated electric range above its current 38 miles.

CHARGER

The onboard charger on the 2016 Volt will be "a little" faster than the current 3.3-kW one, but not much. GM said specifically that (DC) fast charging wasn't needed, and that the current charger was satisfactory to its owners.

Company executives said that point is proven by the stats on 120-Volt vs 240-Volt charging.

Nitz noted that GM expected that up to 80 percent of Volt owners would install 240-Volt Level 2 charging stations. In fact, a majority of Volt charging--55 percent--is done using 120-Volt service instead.

That told the team that faster charging just wasn't a high priority for most Volt drivers.

+++++

Overall, the Volt team said that feedback from owners of the first-generation Volt guided the refinements made to the next-generation powertrain.

Two factors surprised the team as real-world data began to filter in from 2011 through 2013, according to Farah and Nitz.

First, the owners "craved" miles driven on electricity--and plugged in much more than the daily overnight recharge that the team had expected.

The average Volt, in fact, is recharged 1.4 times every day, with Volt owners taking advantage of both "opportunistic charging" wherever they find it and charging at workplaces.

Second, the "fluid" and instantaneous experience of electric drive was one of the things the owners prized most--against plug-in hybrids that switched on their engines under maximum power demand.

The "big battery pack" that permitted electric drive for its entire range, without help from the engine, turned out to be a huge selling point.

The team, they said, asked themselves what they could do to increase the electric miles that Volts logged.

Those figures are now roughly two-thirds of overall miles, and about 80 percent of commute miles. What would it take, they asked, to boost commute miles driven on electricity from 80 to 90 percent?

In the end, GM released a lot of technical details without answering the questions that Volt owners most wanted to know: What's the electric range, and what's the fuel efficiency in range-extending mode?

Those numbers will come in about 10 weeks--but not yet.

The new 2016 Chevrolet Volt will go on sale during the second half of 2015.

General Motors provided airfare, lodging, and meals to enable High Gear Media to bring you this first-person report.